Micro-electro-mechanical device with compensation of errors due to disturbance forces, such as quadrature components

ABSTRACT

MEMS device having a support region elastically carrying a suspended mass through first elastic elements. A tuned dynamic absorber is elastically coupled to the suspended mass and configured to dampen quadrature forces acting on the suspended mass at the natural oscillation frequency of the dynamic absorber. The tuned dynamic absorber is formed by a damping mass coupled to the suspended mass through second elastic elements. In an embodiment, the suspended mass and the damping mass are formed in a same structural layer, for example of semiconductor material, and the damping mass is surrounded by the suspended mass.

BACKGROUND

1. Technical Field

The present disclosure relates to a micro-electro-mechanical device withcompensation of errors due to disturbance forces, such as quadraturecomponents.

2. Description of the Related Art

As is known, MEMSs (Micro-Electro-Mechanical Systems) are used in anincreasingly widespread way in different applications, due to theirsmall dimensions, costs compatible with consumer applications, and theirincreasing reliability. In particular, with this technology inertialsensors are manufactured, such as microintegrated gyroscopes andelectro-mechanical oscillators.

MEMSs of this type are generally based upon micro-electro-mechanicalstructures comprising a supporting body and at least one mobile masscoupled to the supporting body through springs or “flexures”. Thesprings are configured for enabling the mobile mass to oscillate withrespect to the supporting body according to one or more degrees offreedom. The mobile mass is capacitively coupled to a plurality of fixedelectrodes on the supporting body, thus forming variable capacitancecapacitors. The movement of the mobile mass with respect to the fixedelectrodes on the supporting body, for example under the action ofexternal forces, modifies the capacitance of the capacitors; thus, it ispossible to detect the displacement of the mobile mass with respect tothe supporting body and the external force. Instead, when suitablebiasing voltages are supplied, for example through a separate set ofdriving electrodes, the mobile mass may be subjected to an electrostaticforce that causes movement thereof.

To obtain micro-electro-mechanical oscillators, the frequency responseof the MEMS structures is usually exploited, which is of a second-orderlow-pass type, and has a resonance frequency.

MEMS gyroscopes, in particular, have a complex electro-mechanicalstructure, which typically comprises at least two masses that are mobilewith respect to the supporting body, coupled to each other so as to havea number of degrees of freedom depending upon the architecture of thesystem. In the majority of cases, each mobile mass has one or twodegrees of freedom. The mobile masses are capacitively coupled to thesupporting body through fixed and mobile sensing and driving electrodes.

In an implementation with two mobile masses, a first mobile mass isdedicated to driving and is kept in oscillation at the resonancefrequency at a controlled oscillation amplitude. The second mobile massis driven with oscillatory (translational or rotational) motion and, incase of rotation of the microstructure about a gyroscope axis at anangular velocity, is subjected to a Coriolis force proportional to theangular velocity itself. In practice, the second (driven) mobile massacts as an accelerometer that enables detection of the Coriolis forceand detection of the angular velocity. In another implementation, asingle suspended mass is coupled to the supporting body to be mobilewith respect to the latter with two independent degrees of freedom, andprecisely one driving degree of freedom and one sensing degree offreedom. The latter may include a movement of the mobile mass in theplane (“in-plane movement”) or perpendicular thereto (“out-of-planemovement”). A driving device keeps the suspended mass in controlledoscillation according to one of the two degrees of freedom. Thesuspended mass moves on the basis of the other degree of freedom inresponse to rotation of the supporting body about a sensing axis,because of the Coriolis force.

As has been mentioned, to enable the MEMS gyroscope to operate properly,a driving force is applied that keeps the suspended mass in oscillationat the resonance frequency. A reading device then detects thedisplacements of the suspended mass. These displacements represent theCoriolis force and the angular velocity and may be detected usingelectrical reading signals correlated to variations of the capacitancebetween the second (driven) mass and the fixed electrodes.

However, MEMS gyroscopes have a complex structure and frequently havenon-ideal electro-mechanical interactions between the suspended mass andthe supporting body. Consequently, the useful signal components aremixed with spurious components, which do not contribute to themeasurement of the angular velocity. The spurious components may dependupon various causes. For instance, manufacturing defects and processspread are potentially inevitable sources of noise, the effect whereofis unforeseeable.

A common defect depends upon the fact that the oscillation direction ofthe driving mass does not perfectly matches the degrees of freedomdesired in the design stage. This defect is normally due toimperfections in the elastic connections between the suspended mass andthe supporting body and causes onset of a force directed along thedetection degree of freedom of the angular velocity. This force in turngenerates an error, referred to as “quadrature error”, due to a signalcomponent of unknown amplitude, at the same frequency as the carrier andwith a phase shift of 90°.

In some cases, the quadrature components are so large that they may notsimply be neglected without introducing significant errors. Normally, atthe end of the manufacturing process, calibration factors are used inorder to reduce the errors within acceptable margins. However, in manycases, the problem is not completely solved, since the amplitude of thequadrature oscillations may vary during the life of the device. Inparticular, the supporting body may be subject to deformations due tomechanical stresses or temperature variations. In turn, the deformationsof the supporting body may cause unforeseeable variations in themovements of the masses and, consequently, in the quadrature components,which are no longer effectively compensated.

BRIEF SUMMARY

One or more embodiments of the present disclosure may reduce theincidence of the quadrature oscillations in MEMS devices as referred toabove.

According to one embodiment of the present disclosure, amicro-electro-mechanical device is provided. In practice, the deviceuses a dynamic absorber that is able to compensate undesired forces,such as quadrature components of inertial systems, which may causeundesired displacements on a suspended mass. To this end, the dynamicabsorber comprises a tuned damping mass, fixed to the suspended mass orsystem of suspended masses and configured to have a natural frequencytuned to the undesired forces to be compensated. In this way, thedamping mass reduces the dynamic response of the suspended mass andstabilizes it.

One embodiment of the micro-electro-mechanical device uses two masses,one of which is mobile with respect to the supporting body and iselastically connected thereto. This mobile mass is coupled to thesubstrate so as to have two degrees of freedom, dedicated, respectively,to driving and movement sensing, here out of the plane, as a result ofthe Coriolis force. The other mass works as a dynamic absorber.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

For a better understanding of the present disclosure preferredembodiments thereof are now described, purely by way of non-limitingexample, with reference to the attached drawings, wherein:

FIG. 1 is a simplified block diagram of a device in accordance with oneembodiment;

FIGS. 2A and 2B shows amplitude and phase Bode diagrams of the transferfunction of the device of FIG. 1;

FIG. 3 shows a schematic embodiment of a structure for compensatingquadrature components for a MEMS microstructure;

FIG. 4 shows a simulation of the movement of the structure of FIG. 3;

FIG. 5A shows a simplified diagram of a possible embodiment of a MEMSgyroscope provided with the compensation structure of FIG. 3;

FIG. 5B is a top plan view of a portion of the gyroscope of FIG. 5A, atan enlarged scale; and

FIG. 6 shows a simplified block diagram of an electronic systemincorporating a MEMS gyroscope.

DETAILED DESCRIPTION

For an understanding of aspects of the present disclosure, referencewill be made to FIG. 1, showing a block diagram of a MEMS device 1, suchas a gyroscope, having two degrees of freedom (even though the followingconsiderations also apply to systems having N degrees of freedom).

FIG. 1 schematically shows a MEMS device 1 represented schematically inits basic elements as regards the dynamic behavior according to onedegree of freedom (displacement along an axis Z in the presence ofundesired components, for example, quadrature components, along thisaxis), thus neglecting any movements in other directions. Theconsiderations hereinafter are thus aimed at highlighting the conditionswhereby the effect of the undesired force in the considered direction iscanceled out.

The MEMS device 1 comprises a suspended mass 2 and a damping mass 3. Thesuspended mass 2 is constrained to a supporting body 4 through a firstsystem of springs 5 having elastic constant k₁ and to the damping mass 3through a second system of springs 6 having elastic constant k₂.

Let F be the quadrature force of a sinusoidal type (F=F₀sen(ωt)) at thedriving frequency ω in the sensing direction Z. The quadrature force Fcauses a displacement of the MEMS device 1 in the sensing direction asdescribed by the following system of equations:

$\begin{matrix}\left\{ \begin{matrix}{{{m_{1}{\overset{¨}{z}}_{1}} + {k_{1}z_{1}} + {k_{2}\left( {z_{1} - z_{2}} \right)}} = {F_{0}{\sin \left( {\omega \; t} \right)}}} \\{{{m_{2}{\overset{¨}{z}}_{2}} + {k_{2}\left( {z_{2} - z_{1}} \right)}} = 0}\end{matrix} \right. & (1)\end{matrix}$

where z₁ is the displacement of the suspended mass 2, z₂ is thedisplacement of the damping mass 3, and k₁, k₂ are the elastic constantsof the springs.

The solution of the system (1) is given by displacements of a sinusoidaltype:

z ₁(t)=Z ₁ sin(ωt)

z ₂(t)=Z ₂ sin(ωt)

Setting, for simplicity:

$\omega_{22} = \sqrt{\frac{k_{2}}{m_{2}}}$$\omega_{11} = \sqrt{\frac{k_{1}}{m_{1}}}$ $Z_{0} = \frac{F_{0}}{k_{1}}$

where ω₁₁ and ω₂₂ are the natural frequency of the suspended mass 2 andthe natural frequency of the damping mass 3, and substituting z₁, z₂,F₀, ω₁₁ and ω₂₂ in Eq. (1), we obtain

$\begin{matrix}\left\{ \begin{matrix}{{{\left\lbrack {1 + \frac{k_{2}}{k_{1}} - \left( \frac{\omega}{\omega_{11}} \right)^{2}} \right\rbrack Z_{1}} - {\frac{k_{2}}{k_{1}}Z_{2}}} = Z_{0}} \\{{{- Z_{1}} + {\left\lbrack {1 - \left( \frac{\omega}{\omega_{22}} \right)^{2}} \right\rbrack z_{2}}} = 0}\end{matrix} \right. & (2)\end{matrix}$

Solving the system of equations (2) for Z₁ and Z₂ and normalizing themwith respect to Z₀ (as defined above) we obtain:

$\quad\left\{ \begin{matrix}{\frac{Z_{1}}{Z_{0}} = {\frac{1 - \left( \frac{\omega}{\omega_{22}} \right)^{2}}{{\left\lbrack {1 + \frac{k_{2}}{k_{1}} - \left( \frac{\omega}{\omega_{11}} \right)^{2}} \right\rbrack \left\lbrack {1 - \left( \frac{\omega}{\omega_{22}} \right)^{2}} \right\rbrack} - \frac{k_{2}}{k_{1}}}\mspace{205mu} \left( {3a} \right)}} \\{\frac{Z_{2}}{Z_{0}} = {\frac{1}{{\left\lbrack {1 + \frac{k_{2}}{k_{1}} - \left( \frac{\omega}{\omega_{11}} \right)^{2}} \right\rbrack \left\lbrack {1 - \left( \frac{\omega}{\omega_{22}} \right)^{2}} \right\rbrack} - \frac{k_{2}}{k_{1}}}\mspace{205mu} \left( {3b} \right)}}\end{matrix} \right.$

From Eq. (3a) it may be noted that the displacement of the mass m₁(suspended mass 2 of FIG. 1) may be made zero (Z₁=0) when ω=ω₂₂, i.e.,when the device 1 is driven at the natural frequency of the damping mass3. The Bode diagram of the transfer function Z₁/Z₀ described by Eq. (3a)is shown in FIGS. 2A and 2B. As may be noted:

At the natural frequency ω₂₂ of the damping mass 3, the amplitude of thedisplacement X₁ of the suspended mass 2 due to the quadrature force Fhas a minimum;

Two peaks exist at the sides of the natural frequency ω₂₂ andcorrespond, respectively, to an in-phase mode 15 and to aphase-opposition mode 16, wherein the suspended mass 2 and the dampingmass 3 move, with respect to the center, in phase or in phase oppositionwith respect to each other;

The relative displacement Z₂/Z₀ of the damping mass 3 at its naturalfrequency ω₂₂ is equal to the ratio of the elastic constantsZ₂/Z₀=k₁/k₂;

The damping mass 3 dampens the amplitude of oscillation Z₁ of thesuspended mass 2; and

At the natural frequency ω₂₂ of the damping mass 3, the suspended mass 2is subjected to a system of forces with zero resultant along the sensingdirection Z.

Consequently, by actuating the MEMS device 1 at the natural frequencyω₂₂ of the damping mass 3, the suspended mass 2 does not undergodisplacements in the considered direction caused by the quadratureforce. In practice, the damping mass 3 operates as notch filter ordynamic absorber, analogously to the known solutions for stabilizingskyscrapers and antiseismic buildings.

This behavior may be exploited in a MEMS device when it is desired toprevent spurious displacements in the sensing direction.

FIGS. 3 and 4 show a possible embodiment of the quadrature componentdamping solution in a generic MEMS device 10.

Here, the suspended mass 2 surrounds the damping mass 3 and is anchoredto a supporting body 11 (FIG. 4) via anchorage regions 12 and the firstsprings 5. As in FIG. 1, the suspended mass 2 is elastically coupled tothe damping mass 3 through the second springs (coupling springs) 6. Thesecond springs 6 are also comprised within the overall dimensions of thesuspended mass 2 and are arranged between the latter and the dampingmass 3.

The suspended mass 2 and the damping mass 3 are formed in the samestructural layer 14, for example of semiconductor material, such asmono- or polycrystalline silicon, and are suspended over the supportingbody 11, for example a substrate of semiconductor material, such asmonocrystalline silicon.

The suspended mass 2 is driven in the direction of the arrow 7(direction X) and, due to the springs 5, may move in the direction Z(sensing direction). To this end, fixed electrodes (not shown) areformed over the supporting body 11 and capacitively coupled to thesuspended mass 2, in a known manner.

As explained previously, as a result of the quadrature error, anundesired force acts on the masses 2 and 3 in a direction Zperpendicular to the plane of the masses 2, 3. Due to the presence ofthe damping mass 3 and by driving the suspended mass 2 at the naturalfrequency ω₂₂ of the damping mass 3, this force is compensated for onthe suspended mass 2 and does not cause, to a first approximation, adisplacement thereof in the direction Z. Instead, the damping mass 3undergoes a movement having a component along the axis Z, as shown inFIG. 4. In this way, any movements in the direction Z of the suspendedmass 2 are due to different external forces and may thus be detectedwithout substantial errors.

An embodiment of a gyroscope using the operating principle describedabove is shown in FIG. 5A. FIG. 5A shows a gyroscope 20 having foursensing masses 21-24 supported by first, second, and third anchorageregions 25A, 25B and 25C. The support regions 25A, 25B and 25C may beconnected to a semiconductor substrate, for example of monocrystallinesilicon, not shown in the figures, similar to the supporting body 11 ofFIG. 4.

The mobile masses 21-24, all of doped semiconductor material such aspolycrystalline silicon, are defined by respective plates having asubstantially trapezoidal shape, arranged symmetrically in pairs withrespect to a center C of the gyroscope 20 and parallel, in restcondition, to the drawing plane (plane XY). In particular, a firstsensing mass 21 and a second sensing mass 23 are driven along a firstdriving axis D1 and are arranged symmetrically to each other withrespect to a second driving axis D2, perpendicular to D1. A thirdsensing mass 22 and a fourth sensing mass 24 are arranged symmetricallyto each other with respect to the first driving axis D1 and are drivenalong the second driving axis D2.

The first and second sensing masses 21, 23 are connected to the firstanchorage regions 25A through first elastic springs 30. The third andfourth sensing masses 22, 24 are connected to the first and secondanchorage regions 25A, 25B through two driving structures 27 arrangedlaterally and externally (with respect to the center C) to the third andfourth sensing masses 22, 24. In detail, the third and fourth sensingmasses 22, 24 are connected to the driving structures 27 through secondelastic springs 31, and the driving structures 27 are connected to thefirst and second anchorage regions 25A, 25B through third and fourthelastic springs 32, 33. The first and second sensing masses 21, 23 arefurther connected to the driving structures 27 through fifth elasticsprings 35. Finally, the sensing masses 21-24 are coupled to a centralbridge 26, with a square annular shape, through sixth elastic springs36. The central bridge 26 is in turn coupled to the third anchorageregion 25C through seventh elastic springs 37.

The elastic springs 30-37 are configured to provide the sensing masses21-24 with two degrees of freedom with respect to the support regions25A-25C. More precisely, the fifth elastic springs 35 are configured tocause the first and second sensing masses 21 and 23 to translate alongthe first driving axis D1, whereas the third elastic springs 33 areconfigured to cause the third and fourth sensing masses 22 and 24 totranslate along the second driving axis D2. The first, fifth, and sixthsprings 30, 35 36 further enable the first and second sensing masses 21and 23 to tilt about respective sensing axes A1, A2 parallel to eachother and perpendicular to the first driving axis D1. The second andsixth springs 32, 36 further enable the second and fourth sensing masses22 and 24 to tilt about respective sensing axes A3, A4 parallel to eachother and perpendicular to the second driving axis D2.

The driving axes D1, D2 and the sensing axes A1-A4 are all parallel toplane XY.

The central bridge 26 is defined by a rigid semiconductor element,having a substantially hollow quadrangular shape, and is in turnindependently tiltable about the first and second driving axes D1, D2.In this way, the first and second sensing masses 21, 23 both rotateclockwise or both counterclockwise about the respective sensing axes A1,A2. Likewise, the third and fourth sensing masses 22, 24 both rotateclockwise or both rotate counterclockwise about the respective sensingaxes A3, A4. That is, the first, second, third, and fourth sensingmasses 21, 22, 23, 24 rotate in and out of the page.

The driving structures 27 are here each formed by two driving units 47and by a drive detection unit 38. The units 38 are formed by sets offixed electrodes 40 and mobile electrodes 41, mutually comb-fingered, asshown in FIG. 5B. The fixed electrodes 40 are connected to the substratein a way not shown. The mobile electrodes 41 are connected to a mobileframe 43 for each driving structure 27, the frame being connected to thesensing masses 21-14 in the way described above.

In particular, and in a known way, the electrodes 40, 41 of the drivingunits 47 are biased so as to generate electrostatic, attraction orrepulsion forces between the fixed and mobile electrodes 40, 41. Theseforces cause a movement of the mobile frames 43 in the direction of thesecond driving axis D2. As referred to above, this movement of themobile frames 43 is transferred directly and parallel to the second andfourth sensing masses 22, 24 and, as a result of the configuration ofthe sixth elastic springs 35, perpendicularly to the first and thirdsensing masses 21, 23.

In a per se known manner, the drive detection unit 38 detects, throughits own fixed electrodes 55 and mobile electrodes 56, the effectivemovement imparted by the driving units 47 in order to ensure a precisecontrol.

In a way known and not shown, sensing electrodes are formed on thesubstrate, under the sensing masses 21-24, to detect the movementthereof in the direction Z.

Each sensing mass 21-24 further carries a respective damping mass 45. Asin the case of FIG. 3, each damping mass 45 is formed within theperimeter of the respective sensing mass 21-24 and is elasticallycoupled thereto through bilateral springs 46, corresponding to thesecond springs 6 of FIG. 3.

The damping masses 45 are equal, and are provided in a same structurallayer, for example a polysilicon layer, and are all supported in thesame way, so as to have the same natural frequency ω₂₂.

As discussed above, by biasing the driving units 47 in such a way thatthe fixed electrodes 41 and mobile electrodes 42 attract and repel eachother with a frequency (driving frequency) equal to the naturalfrequency ω₂₂ of the damping masses 45 (notch frequency), the sensingmasses 21-24 do not undergo a displacement in the respective sensingdirection along axis Z due to the quadrature forces. It follows that thereading is not affected by quadrature components.

In use, the drive detection unit 38 is connected to a control circuit(not shown), for example, formed together with the control and readingalgorithms of the gyroscope 20 in an ASIC (Application-SpecificIntegrated Circuit), which enables, in closed loop, a precise control ofthe driving frequency for keeping it equal to the notch frequency orwithin a preset range of variability.

Use of a tuned mechanical damping filter thus enables a reduction of theamplitude of the oscillations caused by the quadrature force and otherexternal mechanical forces at the preset frequency. In the specific caseof the gyroscope, there are two main advantages:

the electrical signal to be compensated, due to the quadrature forces,is considerably lower than in known implementations; this results in areduction of the consumption of the ASIC compensation chain and of theoutput noise;

the variations due to the deformations of the structure during theuseful life of the device are reduced in proportion, since the amplitudeof the quadrature component is reduced.

The implementation of the mechanical filter does not entail variationsin the manufacture steps of the microstructure, but an appropriatedesign and modification of the layout thereof are sufficient.

Control of the driving frequency is simple. In some cases, no additionalcomponent is required since at times MEMS structures already have adriving control system. In any case, insertion of the drive detectionunit 38 does not entail any re-design of the MEMS structure, and theroutine for controlling the oscillation frequency may be integrated inthe ASIC.

FIG. 6 illustrates a portion of an electronic system 100 according to anembodiment of the present disclosure. The system 100 incorporates thegyroscope 20 and may be used in devices such as, for example, a tablet,a laptop, or a portable computer, for example with wireless capacity, asmartphone, a wearable device, a messaging device, a digital musicplayer, a digital photo or video camera, or other device designed forprocessing, storing, transmitting, or receiving information. Forinstance, the gyroscope 20 may be used in a digital videocamera todetect movements and carrying out image stabilization. In otherembodiments, the gyroscope 20 may be included in a portable computer, aPDA, or a smartphone for detecting a free-fall condition and activatinga safety configuration or for activating or controlling functions basedupon motion of the device. In a further embodiment, the gyroscope 20 maybe included in a motion-activated user interface for computers orconsoles for videogames. Again, the gyroscope 20 may be incorporated ina satellite-navigation device and be used for temporarily tracking ofthe position in case of loss of the satellite-positioning signal.

The electronic system 100 may comprise a controller 110, an input/outputdevice 120, for example, a keyboard or a display, the MEMS device 1, awireless interface 140, and a memory 160, of a volatile or non-volatiletype, coupled together through a bus 150. In one embodiment, a battery180 may supply the system 100. It should be noted that the scope of thepresent disclosure is not limited to embodiments that necessarily haveone or all of the mentioned devices.

The controller 110, for example, may comprise one or moremicroprocessors, microcontrollers, and the like. The controller 110 may,for example, be formed in an ASIC and include the components andalgorithms for controlling the drive frequency on the basis of thesignals supplied by the drive detection unit 38.

The input/output device 120 may be used for generating a message. Thesystem 100 may use the wireless interface 140 for transmitting andreceiving messages to and from a wireless communication network withradiofrequency signal. Examples of wireless interface may comprise anantenna, a wireless transceiver, such as a dipole antenna, even thoughthe disclosure is not limited thereto. Furthermore, the input/outputdevice 120 may supply a voltage representing what is stored in digitalor analogue form.

Finally, it is clear that modifications and variations may be made tothe solution described and illustrated herein, without thereby departingfrom the scope of the present disclosure.

In particular, the use of a mechanical filter of the described type maybe implemented in various types of MEMS microstructures of an inertialtype.

Furthermore, this solution may be applied to microstructures with adifferent number of degrees of freedom by providing each degree offreedom with an appropriate tuned damper.

The various embodiments described above can be combined to providefurther embodiments. These and other changes can be made to theembodiments in light of the above-detailed description. In general, inthe following claims, the terms used should not be construed to limitthe claims to the specific embodiments disclosed in the specificationand the claims, but should be construed to include all possibleembodiments along with the full scope of equivalents to which suchclaims are entitled. Accordingly, the claims are not limited by thedisclosure.

1. A MEMS device comprising: a substrate; first elastic elements; and a movable mass system including: a suspended mass elastically coupled to the substrate by the first elastic elements and subject to disturbance forces along a vibration direction; and a dynamic absorber elastically coupled to the suspended mass and configured to reduce movements of the suspended mass due to the disturbance forces.
 2. The MEMS device according to claim 1, wherein the disturbance forces are quadrature forces that act on the suspended mass in the vibration direction at a natural oscillation frequency of the dynamic absorber.
 3. The MEMS device according to claim 2, wherein the dynamic absorber comprises a damping mass coupled to the suspended mass by second elastic elements, the first and second elastic elements being configured to enable the suspended mass and the damping mass to move in the vibration direction.
 4. The MEMS device according to claim 3, wherein the damping mass is surrounded by the suspended mass.
 5. The MEMS device according to claim 4, wherein the damping mass and the suspended mass are formed in a structural layer of semiconductor material.
 6. The MEMS device according to claim 5, wherein the structural layer is suspended over the substrate, wherein the substrate is of semiconductor material.
 7. The MEMS device according to claim 1, wherein the MEMS device forms an inertial sensor.
 8. The MEMS device according to claim 7, comprising third elastic elements and a driving structure coupled to the suspended mass by the third elastic elements, the driving structure being configured to generate a driving movement in a driving direction that is different from the vibration direction at the natural oscillation frequency.
 9. The MEMS device according to claim 7, wherein the inertial sensor is a gyroscope.
 10. The MEMS device according to claim 9, wherein: the gyroscope is a biaxial gyroscope, the suspended mass comprises first and second pairs of sensing masses arranged symmetrically about a first and a second driving axes; the sensing masses being arranged about a central axis and being elastically coupled to a central anchorage region; the first and second driving axes being perpendicular to each other, the sensing masses of a first pair being symmetric with respect to the second driving axis and being actuated parallel to the first driving axis, the sensing masses of a second pair being symmetric with respect to the first driving axis and being actuated parallel to the second driving axis; and each sensing mass surrounding and elastically coupled to a respective damping mass.
 11. The MEMS device according to claim 10, comprising: fourth and fifth elastic elements; a first driving frame and a second driving frame elastically coupled to the substrate, the first and second driving frames being elastically coupled to the first pair of sensing masses by the fourth elastic elements and configured to transmit a driving movement along the first driving axis, the first and second driving frames being elastically coupled to the second pair of sensing masses by the fifth elastic elements and configured to transmit a driving movement along the second driving axis.
 12. The MEMS device according to claim 11, wherein the first and second driving frames each include at least one electrostatic driving unit configured to generate a driving movement for the respective driving frame at a natural oscillation frequency of the damping masses, each of the first and second driving frames including a frequency-detection unit configured to detect an effective driving frequency of the sensing masses.
 13. An electronic device comprising: a controller; an input/output device coupled to the controller; and a MEMS device coupled to the controller, the MEMS device including: a substrate; first and second elastic elements; and a movable mass system including: a suspended mass elastically coupled to the substrate by the first elastic elements; and a dynamic absorber elastically coupled to the suspended mass by the second elastic elements, the dynamic absorber being configured to absorb at least some disturbance forces that would otherwise act on the suspended mass.
 14. The electronic device according to claim 13, wherein the dynamic absorber is located in an opening of the suspended mass.
 15. The electronic device according to claim 13, wherein MEMS device includes a driving assembly configured to drive the suspended mass and the damping mass in a first plane, wherein the damping mass is driven at its resonance frequency, wherein the disturbance forces are perpendicular to the first plane.
 16. The electronic device according to claim 13, wherein the MEMS device includes at least one of a gyroscope and accelerometer.
 17. The electronic device according to claim 13, wherein the electronic device is at least one of a tablet, a laptop, a portable computer, a smartphone, a wearable device, a messaging device, a digital music player, and a digital photo or video camera.
 18. The electronic device according to claim 13, wherein the suspended mass extends substantially in a plane, and the dynamic absorber is configured to absorb disturbance forces having a direction that is perpendicular to the plane of the suspended mass.
 19. The electronic device according to claim 13, wherein: the suspended mass comprises first and second pairs of sensing masses arranged symmetrically about a first and a second driving axes, respectively; the first and second driving axes being perpendicular to each other, the sensing masses of a first pair being symmetric with respect to the second driving axis and being actuated parallel to the first driving axis, the sensing masses of a second pair being symmetric with respect to the first driving axis and being actuated parallel to the second driving axis; and each sensing mass surrounding by and being elastically coupled to a respective damping mass.
 20. The electronic device according to claim 13, wherein the sensing masses being arranged about a central axis and being elastically coupled to a central anchorage region. 